I will be flying out of Toronto Pearson (YYZ) to Minneapolis - Saint Paul (MSP) where I will transferring to a flight for Rochester MN (RST). My layover will be 3 hours, which I understand will be enough time. What should I be prepared to do as I switch planes? Will I be questioned about my travels again? Will my luggage need to be scanned, etc. again? I will appreciate any tips/ advice for a first-time flyer. Thanks!
YYZ is a US Preclearence airport, which means you'll go through US immigration and customs in Toronto before you board your first flight. If you have booked this all as a single transaction on a single ticket, your bags should be checked through to Rochester, which you can confirm with the agent who tags them at check-in in Toronto. (If you've booked two separate tickets for these flights, you'll have to exit the secure area, claim your luggage in Minneapolis, check it in again, and go through security.)
Since you've already been admitted to the US in Toronto, your flight will arrive into MSP as a normal domestic flight. Assuming you've booked a single ticket, the only thing you'll need to do is walk to the gate for your next flight before boarding closes. Unless your flight is significantly delayed, three hours is plenty of time.